Summary Lufthansa Airlines flight 8161 (DLH8161), a MD-11, was en route from JohnF. Kennedy International Airport, New York, USA, to Frankfurt/Main International Airport, Germany, via the TUSKY intersection direct to 48 north 050 west, at flight level330. DLH8161 was expecting a clearance to climb to FL350 for the oceanic crossing. Continental Airlines flight65 (COA65), a Boeing757-224, was en route from Lisboa, Portugal, to Newark, New Jersey, USA, via 48 north 050 west direct the Torbay very high frequency omni directional range direct TUSKY intersection, at flightlevel330. When the aircraft were approximately 100 nautical miles apart, the controller issued a climb clearance to DLH8161 to provide the required separation. However, the radio frequency used to communicate with DLH8161 had failed as a result of a problem in the landline connecting Gander Area Control Centre with the peripheral station used for radio transmissions, and the clearance did not reach the crew. The aircraft were approximately 30nm apart before radio contact was restored using alternate means, and the controller cleared DLH8161 to climb to flight level350. At about the same time, a supervisory controller, using a backup radio, issued a clearance to COA65 to descend to flight level320. The aircraft had four nautical miles lateral and 3000feet vertical spacing when they passed, at approximately 1200 Newfoundland standard time. The radar separation minima of five nautical miles lateral or 1000feet vertical between the aircraft was not assured until after radio contact was restored. Ce rapport est galement disponible en franais. Other Factual Information At the time of the occurrence, the Gander, Newfoundland and Labrador, high domestic airspace comprised four sectors. The occurrence took place in the most southerly sector which extended horizontally from St.Anthony, Newfoundland and Labrador, to the southern boundary of Gander controlled airspace, a distance of approximately 450nm, and vertically above flight level (FL)280. This airspace was south of and outside of that day's organized track structure, and contained a mixture of eastbound and westbound traffic. A single controller was responsible for this sector, which was the normal practice in this specialty. The traffic level was moderate with some complexity. From the time communication with Lufthansa Airlines flight8161 (DLH8161) was lost until it was re-established, the Gander controller (controller), who had qualified in the specialty two months previously, was controlling and coordinating the movement of 15aircraft. The supervisor was in the high domestic specialty at the supervisor's position and was not aware of the communications failure until informed by the controller approximately 10minutes after radio contact was lost. When DHL8161 initially contacted the controller at 1128 Newfoundland standard time1, on frequency 134.7megahertz (MHz), the aircraft was cruising at FL330 eastbound toward the COLOR intersection. The flight had a clearance for the oceanic crossing which included a remark to expect FL350. The controller cleared DLH8161 to fly direct to 48 north 050 west, which shortened the aircraft's route to the oceanic entry point and would take the aircraft approximately 12 nm south of the Torbay VOR. The controller was primarily using radar separation minima in the airspace under his control. One of the stipulations for applying radar separation is the requirement for direct pilot-to-controller communications. COA65, flying westbound at FL330, was approaching the boundary between oceanic and domestic airspace at 48 north 050 west. The crew had been instructed to contact the controller at this point on frequency 134.7MHz. Aircraft entering Gander domestic airspace from oceanic airspace are not radar identified until after direct communications is established with the controller. At 1147, in order to establish vertical separation between the aircraft, the controller cleared DLH8161 to FL350 (seeAppendixA), but received no readback from the crew. Over the next eight minutes, the controller attempted to contact DLH8161 on 134.7MHz nine times, but did not receive a response. DLH8161 was not observed to change altitude and remained at FL330. The most common occurrences of communication failures at Gander ACC are linked to problems with the aircraft. At 1148, a Moncton Area Control Centre (ACC) controller advised the controller that another flight had returned to Moncton's frequency after being sent to the Gander frequency 134.7MHz because it had not received a response on the assigned frequency. The controller advised Moncton ACC to again send that aircraft over to 134.7MHz, and if no success, to ask the aircraft to try 132.05MHz. The controller also attempted to contact several other flights in the southern portion of the sector that were expected to be monitoring 134.7MHz, but received no answer. The controller contacted the coordinator of the International Flight Service Station (IFSS) and determined that DLH8161 had not contacted the IFSS. At 1155:03, the controller requested a westbound aircraft in the vicinity, and operating on another frequency, to switch to the guard frequency (121.5MHz), attempt to contact DLH8161 and COA65, and request that they contact Gander ACC. The controller did not specify a frequency for the aircraft to use. A short time later the controller initiated a second call to the IFSS coordinator and requested him to contact DLH8161 using a SELCAL2 and request the pilot to contact Gander ACC on frequency 133.9MHz. The controller also requested that the IFSS coordinator send COA65 to the controller's frequency early. The controller then advised the Gander high domestic supervisor that he was unable to contact DLH8161. The supervisor walked to the controller's work position and observed, from the controller's voice switch communications system (VSCS) communications control panel (CCP) display, that the controller's transmissions on 134.7MHz were not going out to the aircraft (seeFigure1). The supervisor contacted the IFSS coordinator to re-confirm that they were not in communication with DLH8161 or COA65. The supervisor then used a multi-channel, tunable, back-up radio and was able to communicate with COA65 on 134.7MHz. At 1155:22, the supervisor cleared COA65 to descend immediately to FL320, which was acknowledged by the crew. Recorded radar information indicates that COA65 commenced descent at 1156. COA65 was not instructed to change to a serviceable main frequency after the supervisor issued the descent clearance, and the back-up radio was left unmonitored. At 1156:03, DLH8161 contacted the controller on frequency 133.9MHz and was immediately instructed to climb to FL350. The crew of DLH8161 acknowledged the clearance and at 1156:15 recorded radar information indicated that DLH8161 commenced the climb. The controller had not been able to communicate with either aircraft for the previous eight minutes. The aircraft had been closing at a rate of 16nm per minute on nearly reciprocal tracks. Twenty seconds after DLH8161 commenced a climb, the minimum vertical separation of 1000feet was achieved. COA65 and DLH8161 had closed to within 18nm. From 1157 to 1159 the controller continued to try to contact COA65 several times on 134.7MHz, but did not receive a response. At 1159:56, the controller requested another aircraft in the vicinity to contact COA65 on frequency 134.7MHz and instruct the crew to contact Gander ACC on 132.05MHz. COA65 contacted the controller at 1201:22 on 132.05MHz and was instructed to change the transponder code to a discreet value in preparation for radar identification. As a result of the occurrence, a change of controllers at the high domestic position was completed at 1204:29, and COA65 was subsequently radar identified. During the handover briefing, a problem with a frequency was mentioned, but alternate action to restore communications with all aircraft was not discussed. The supervisor advised the technical personnel of a problem with frequency 134.7MHz at approximately 1200. Internal checks completed by the technical staff confirmed that there was a fault in the lines connecting the ACC to the peripheral station (PAL) site at Trepassey; there was no fault found in the main or back-up radios located at the PAL site. There is no alarm that activates in Gander ACC to warn technical staff of this type of failure. The company that maintains the link between Gander ACC and the PAL site was contacted at 1234. The lines between the ACC and the Trepassey PAL site became serviceable at 1237 while the NAV CANADA technician was discussing the outage with a company representative. No reason for the failure has been found. The VSCS is the primary interface for controllers to access the radios and landlines. The VSCS CCP is a display module (seeFigure1) located at each control position. The CCP is a touch sensitive screen which displays all the air/ground frequencies and landlines available to controllers. Each frequency is displayed separately on the screen by a rectangular icon. Different sections of the frequency icon show green depending on what the controller is doing: receiving, transmitting or has pressed the 'press to talk' switch but no transmission occurs (this indicates that there is a fault). Figure1.Voice switch communications system communications display panel The VSCS training provided to controllers included both classroom instruction and hands-on practice. The controller involved in this incident was not aware that the specific green pattern in the frequency icon for 134.7MHz indicated that he was not actually transmitting on that frequency, even though he had depressed the 'press-to-talk' switch. This was the only direct indication to the controller that there was an air traffic control (ATC) communications equipment failure. During the investigation it was determined that some other controllers were also not aware of the significance of the various green light indications on the CCP. A number of frequencies available to Gander ACC controllers are strategically located at PAL sites to ensure that radio communications are available over the entire airspace for which Gander ACC has jurisdiction. The radios have a range of approximately 200nm, depending partly on the aircraft's altitude. The Trepassey PAL site is situated so as to provide radio communications to aircraft flying through the southern portion the airspace controlled by Gander ACC. NAV CANADA has contracted a commercial service provider to maintain the links between the PAL sites and Gander ACC. Both the VSCS and ACC Emergency Communications System (ACCECS)3 are linked to the main and back-up radios at the PAL sites through these links. A level of redundancy is provided in the connection modes (i.e., land line or microwave) between Gander ACC and most PAL sites. The landlines between the Gander ACC and the Trepassey PAL site are routed through St. John's, Newfoundland and Labrador, and only a single line per frequency is available for the portion from St. John's to Trepassey. It was determined that the connection between Gander ACC and St.John's was working, but a failure had occurred in the line between St.John's and Trepassey. As a result, the frequency 134.7MHz, located at Trepassey, was not available to the controller. Both 134.7MHz and 132.05MHz are located at the Trepassey PAL site and are connected to Gander ACC by separate communications links. The transmitter and receiver for 133.9MHz, the frequency on which DLH8161 eventually contacted Gander, is located at Gander. A separate multi-channel, tunable, radio was available at Gander ACC for use in the event of a communications failure; however, not all Gander controllers were aware of its availability, location, or coverage area. The Air Traffic Control Manual of Operations(ATC MANOPS), Section6, describes the procedures for controllers to follow when it is determined that a communications failure has occurred with an aircraft. Controllers receive classroom instruction during both the initial and regional ATC training courses on how to deal with communications failures, including alternate methods of restoring communications with aircraft. The emphasis is on communications failures which originate with the aircraft. During training sessions at Gander ACC, there is no simulation of a communications failure of the ATC portion of the equipment, nor is this type of communications failure procedure reviewed during refresher training. ATC MANOPS does not provide specific direction to controllers in the event that there is a communications failure due to ATC related equipment problems. Another NAV CANADA publication, the Flight Services Manual of Operations (FS MANOPS), Section1112, provides specific steps that flight services specialists should follow if they are unable to contact an aircraft after calling the frequencies on which the aircraft is believed to be listening. Controllers do not normally reference this publication.